So, our gaming group has been playing Godslayer and having a great time so far.

However, we recently got into a debate in regards to the charging concept of Godslayer and would like some clarification.

Version A) A model/unit has to charge towards an enemy & can move up to his full charge range & has to stay engaged.

Impression of this is you can NOT sling past a model. Basically so if you charge at an angle eventually you cross a threshold that you would start moving away from the model is when you stop even if you have more movement, due to the & clause.

Version B) A model/unit charges towards and enemy but can move his full charge range so long as he stays engaged.

Basically the meaning of this is that you can charge past the model ala Warmachine style charging, so in effect it lets you get more models into contact with the model getting charged.

Due to the nature of Godslayer I feel version A is the proper method, that basically means you can't charge past the initial 180 degree arc of the base. However, a clarification would be great since playing it as B would let 2-3 more models get into the fight on a single model.

As long as you move in a straight line, you can do whatever you want with your full charge range, as long as you end up in melee range of the charged enemy model. I can't find anything else in the charge rules. The main point is the straight line. So, charging in a curve is not possible but everything else seems to be ok.

Khazrak and HowNot are absolutely right. There is no front arc limiting LOS or charging options, you can charge in any given direction, as long as you charge in a straight line. Furthermore, you can move as far as you like, as long as you a) move in a straight line and b) engage the declared target model of your charge at the end of your charge movement. That means you can also charge past the base of a target model and get "behind it" (there is no back arc), as long as you don't move out of melee range once you got into it during the charge movement.
So it comes down to your option B, if I get you right.

I think, the 180° arc in this question meant something else and that is the half of the charged model, that is pointing towards the charger. As soon as you leave the front half of the charged model, one could argument, that you are from now on moving further away from the target of the charge and thus could make an illegal move. However, that is not the case ruleswise and so no problem.

Well, technically, as written it is a problem.
pg. 64
"Charging model must always move in a direct line towards the declared target of their charge, and may move any distance up to their total charge movement"

As written, at some point you could feasibly depending on the total charge movement actually start moving away from the model, that is no longer towards. It's something of a if direction is true and distance is true then charge works, if any one if false then you have to stop or fail.

I realize this whole thing is very nitpicky but it can matter for potential damage output.

Edit: The 180 facing concept is just a geometric determination to when you start moving away from the model, I fully realize they have a 360 vision.